The invention relates to a filling apparatus for the introduction of bone cement into the intramedullary cavity of a bone, preferably into the cavity of a femur bone, with a filling cannula, at the end of which a hose-like sleeve is fastened which can be radially expanded under the pressure of emerging bone cement.
Filling apparatuses are described in EP-A-0 628 295. Flexible extensions of a filling cannula are shown there as sleeves, which have a material reserve at their free end which is formed by overlapping elasticity or folding. Filling apparatuses of this kind have the disadvantage that, when the filling cannula is being moved into the intramedullary cavity, they encounter the cavity wall with the jacket edge before the actual end of the cavity is reached. In the event that the sleeve is too stiff, there is the problem that its elasticity is not sufficient to produce a sufficient sealing pressure at a widening cavity cross-section during the filling of the intramedullary cavity. It is also not of much use if the diameter of the filling cannula and the sleeve is chosen to be particularly small, since new problems arise thereby. On the one hand, the expulsion is made more difficult due to the continuously increasing viscosity of the bone cement, and on the other hand, even higher requirements are placed on the sleeve with respect to stretching.
Other embodiments, such as GB-A-2 105 198, presuppose additional elements such as axially displaceable protective sleeves on a filling cannula the end of which is formed as an erectible umbrella with ribs and films lying between them.